The present invention relates to an electric shutter circuit for a camera using a digital regeneration system, wherein a number of pulses corresponding to the brightness of a photographed body is counted and stored in a counting circuit, and the exposure time is automatically controlled in accordance with the stored number of pulses, and wherein the reading out of the stored pulses and shutter opening are synchronized.
An electric shutter circuit for a camera using a digital regeneration system has already been proposed and is constructed so that a light coming from a photographed body passes through a photographying lens, and the brightness of the photographed body is measured with a photoelectric element, and a single pulse having a pulse width inversely proportional to the brightness of light from the photographed body is developed. Standard pulses produced from a pulse generator during only this period are counted and stored in a counting circuit. In synchronism with the start of shutter opening, the memory value stored pulses are successively called out, and by detecting the time point when the calling-out is completed, the shutter is made to close. It is, however, difficult in this structure to synchronize the shutter opening time with the memory value calling-out time, because of the presence of fluctuation in the period of actuation of the timing switch that acts upon the start of shutter opening. Particularly in a circuit of the digital memory value calling-out time are made to synchronize, there is a difficulty at the time of regeneration in changing the frequency of calling-out phase or counting additional or reading-out pulses numbers in the counting circuit. It may be considered to provide a mechanical adjusting mechanism, but this leads to disadvantages of complicated structure and so on.